Control valve apparatus

ABSTRACT

The invention relates to a control valve apparatus ( 1 ) providing reciprocal motion, comprising a spool ( 2 ) and sleeve ( 3 ), a passage ( 4 ) for fluid, which is hydraulic fluid in the embodiment, the passage ( 4 ) being openable and closable by the spool ( 2 ) and sleeve ( 3 ), ports (A, B, C) for fluid, and at least one seal ( 5, 6 ), the arrangement being such that a seat of one seal ( 5 ) reacts with a seat of another ( 6 ) whereby to open the another seal ( 6 ).

The invention relates to a control valve apparatus, particularly tohydraulic directional control valves which in operation allows hydraulicfluid, usually oil, to perform a required function by shutting off onefluid port and opening another.

Such valves are often used in heavy machining, where components arerequired to be moved quickly, with consequent large momentum. Suchvalves therefore often find application in machinery such as a pilinghammer. In such an application, switching of the control valve from onedirection of flow to another is required to take place as quickly aspossible in order to eliminate cavitation beneath a piston and toprevent a high pressure “spike” being generated on the other side of thepiston by the large momentum of the moving parts. The control valve hasto command the hammer to accelerate upwards, to retard it to zerovelocity, and then to drop it under gravitational influence. Theserequirements have been previously achieved by passing metallic pistonrings over open ports using a pair of piston rings, one to close and oneto open. Generally this type of control valve works satisfactorily butit has the disadvantage in that eventually the metallic rings tend tobreak up, especially if no preventative maintenance is performed, andalso to piston rings perform only a partial seal. Pieces of broken ringthen migrate around the system until they finally end up in a filter ofthe system. In the process of such migration much consequential damagecan be effected, leading to excessive downtime for repair andmaintenance, which is expensive on time and equipment.

It is accordingly an object of the invention to seek to mitigate thesedisadvantages.

According to a first aspect of the invention there is provided a controlvalve apparatus providing reciprocal motion, comprising a spool andsleeve, a passage for fluid which is openable and closable by the spooland sleeve, ports for fluid, and at least one seal, the arrangementbeing such that a seat of one seal reacts with a seat of another seal,whereby to open the another seal.

Thus using the invention it is possible to provide substantiallyinstantaneous switching, with no “overlapping” or “underlapping”.

There may be a seat device whereby the spool and sleeve are engageablefor cutting off flow of fluid to the passage. This provides forsubstantially instantaneous cut-off of fluid particularly where the seatdevice may comprise a groove in the spool in which a nose of the sleevemay be received.

The groove and nose may have cooperable sealing surfaces. This seeks toobviate leakage, without requirement for additional seals.

The seating surfaces may be inclined surfaces. This provides for ease ofconstruction, in that machining of the surfaces is relativelystraightforward.

The spool may have a nose adapted for sealing cooperation with a seat ofthe seal, for cutting off fluid flow from the passage to a fluid port.This provides a relatively simple construction.

The seat of the seal and a nose of the spool may have cooperableinclined surfaces for effecting sealing. This again provides forrelative ease of construction.

The ports may have relatively large cross-sectional are in relation tothe fluid flow passage whereby to obviate building up of back fluidpressure. This seeks to ensure instantaneous operation.

There may be a low pressure port, a high pressure inlet port, and apilot pressure inlet port. This arrangement provides for adequatecontrol, particularly when the fluid may be a hydraulic fluid.

The sleeve may have a body, which body may have parts of differentdiameter, whereby a substantially constant (backward) force is appliedto the sleeve, at system pressure. This provides for positive control,particularly when the spool may have a face exposed to hydraulic fluidwhich is of an area to provide substantially constant force to the spoolin the forward direction, at system pressure.

The or each seal may be non-metallic. This arrangement can ensure thateven in the event of failure, migration of valve apparatus seal portswill not cause damage to the apparatus as a whole, particularly when theor each seal may comprise a plastic material.

There may be separate seal(s) and port(s) whereby no port is scanned byany seal.

According to a second aspect of the invention there is provided valveapparatus as hereinbefore defined, in combination with a reciprocabledevice.

The reciprocable device may comprise a hydraulic piling hammer.

Control valve apparatus embodying the invention is hereinafterdescribed, by way of example, with reference to the accompanyingdrawings.

FIG. 1 is a part sectional view of a hydraulic control valve apparatusaccording to the invention, used in a piling hammer, in the restposition.

FIG. 2 shows the valve apparatus of FIG. 1 in the mode of either lifting(retarding) or dropping the hammer; and

FIG. 3 shows the valve apparatus of FIGS. 1 and 2 in the lifting mode.

Referring to the drawings, there is shown a control valve apparatus 1providing reciprocal motion, comprising a spool 2 and sleeve 3, apassage 4 for fluid, which is hydraulic fluid in the embodiment, thepassage 4 being openable and closable by the spool 2 and sleeve 3, portsA, B, C, for fluid, and at least one seat 5, 6, the arrangement beingsuch that a seat of one seal 5 reacts with a seat of another 6 wherebyto open the another seal 6.

In the drawings the arrows ‘R’ show inlet fluid flow, and ‘S’ outletfield flow, shaded areas (FIGS. 2 and 3) showing high pressure fluidareas in the valve apparatus.

There are as mentioned, ports “A”, “B” and “C”, “A” being a low pressureport, “B” a high pressure input or inlet port, and “C” a pilot pressureinput or inlet port. All the ports have a relatively largecross-sectional area in relation to fluid passages of the apparatus,whereby to prevent in the embodiment build-up of back pressure.

The valve apparatus 1 is positioned between an anchor 7 and the backwardor lifting end of the hammer, and a cylinder 8 to which hydraulic fluidflows from the passage 4, to operate the piling hammer.

In the apparatus 1 the spool 2 and sleeve 3 are concentric, the spool 2having a spool nose 9 and inboard thereof a seat device 10 with inclinedseal surfaces in which is received a nose 11 of the sleeve, which sleevenose 11 has an inclined surface complementary to the inclined surface ofthe seat device.

The sleeve and spool are slidable.

There is also a seal device 12 with an inclined surface 13 against whicha complementary inclined surface of the spool nose 9 can seat.

The seal device 12 can include a slidable part 14 which slides adjacentto the seal device 12. A check valve 15 can be mounted under pressure ofa bearing means, such as a spring.

The sleeve 3 has two parts of different diameter, at “X” and “Y”respectively.

In use, and referring firstly to FIG. 1 when high pressure hydraulicfluid is applied at a port B, galleries “D” and “E” fill, and the checkvalve 15 therefore opens marginally (“cracks”) at medium pressure, andstays open. Thus the galleries “D” and “E” are biassed and essentiallyact as hydraulic biassing means, or springs, at the system pressure, inother words the hydraulic pressure applied to the valve 1. The diameter“Y” is greater than the diameter “X”, of the sleeve. Therefore, there isa constant hydraulic pressure (force) in the backward direction (arrow“T”) on the sleeve 3. The area of the face of the spool 2 in the gallery“D” supplies a constant force to the spool in the forward direction(arrow “F”). In FIG. 2, the hammer is either retarding (backwarddirection, arrow “T”), or dropping under gravity (forward direction,arrows R,S). In this situation, hydraulic fluid (usually oil) iscirculated through the valve apparatus as indicated by the arrow R,S.Low pressure is supplied internally through port “A” from an externalsource. The fluid pressure forces in galleries “D” and “E” maintain theengagement of the inclined complementary surfaces of the sleeve andspool at “F”, with a force which is proportional to the hydraulicpressure in the system. To pass from the mode of FIG. 2 to that of FIG.3, that is in a lifting mode of the valve apparatus 1, high pressure isrequired to be supplied to lift and accelerate the hammer. To achievethis, a pilot fluid pressure is supplied through port “C” from anexternal source. This acts on the area of a face of the spool 2 at therear thereof, and decreases the force generated in gallery “E”, whichotherwise acts to maintain the spool; in the FIG. 2 position. The spooland sleeve then move to the loft (forward direction , arrow “F”) asviewed, and the nose 11 of the sleeve 3 engages in the seat device andforces the spool 3 to the left (as viewed) to engage the valve seat at“G” and effect a seal which is energised by force generated in gallery“D”.

At this instant the seal is effected at “G”, the seal at 10 isdisengaged or broken, and allows high pressure oil to pass down thepassage to the cylinder, as indicated by the arrows “R”.

On removal of pilot pressure from port “C”, the sleeve 3 moves in abackward direction until the seal surfaces at 10 engage and the sealsurfaces at “G” are simultaneously disengaged, so the spool and sleevereturn together to the FIG. 2 mode, thus opening ports “A” and “B” forfree flow of low pressure hydraulic oil.

It will be understood that during these operations, galleries “H” and“J” are vented to atmosphere.

It will also be understood that as no ports “A”, “B” or “C” are scannedby seals, all the seals can be non-metallic, which saves on cost, weightand repair.

It will be further understood that using the invention, it is possibleto provide virtually instantaneous switching between forward andbackward movements, and vice-versa, with the following advantages of thevalve apparatus described herein, with reference to the drawings,namely:

1) Instantaneous switching (no overlap or underlap);

2) Large ports pass oil quickly to avoid building back pressure;

3) All seals are non metallic, so that in the event of failure,migration will not cause consequential damaging to the machine as awhole; and

4) The valve has the possibility of zero leakage.

What is claimed is:
 1. A control valve apparatus providing reciprocalmotion between a spool and a sleeve, comprising: the spool; the sleeve;a passage for fluid which can be opened and closed by the spool and thesleeve; ports on the control valve which allow fluid to be provided tothe passage; and at least one seal between a surface of the spool and anose of the spool, wherein a seat of the at least one seal reacts with aseat of another seal, thereby opening the another seal.
 2. The apparatusaccording to claim 1, wherein the spool has a seat device, and whereinthe seat device and the sleeve are engageable for cutting off flow offluid to the passage.
 3. The apparatus according to claim 2, wherein theseat device comprises a groove in the spool in which the nose of thesleeve is received.
 4. The apparatus according to claim 3, wherein thegroove and the nose have cooperable sealing surfaces.
 5. The apparatusaccording to claim 4, wherein the sealing surfaces being inclinedsurfaces.
 6. The apparatus according to claim 3, wherein the spool has anose adapted for sealing cooperation with the seat of at least one seal,for cutting off fluid flow from the passage to a fluid port.
 7. Theapparatus according to claim 6, wherein the seat of at least one sealand a nose of the spool have cooperable inclined surfaces for effectingsealing.
 8. The apparatus according to claim 1, wherein the ports have arelatively large cross-sectional area in relation to the fluid flowpassage whereby the building up of back fluid pressure in the fluid flowpassage is obviated.
 9. The apparatus according to claim 8, wherein theports include a low pressure port, a high pressure inlet port, and apilot pressure inlet port; and wherein the ports have a relatively largecross-sectional area in relation to the fluid flow passage, whereby thebuilding up of back fluid pressure in the fluid flow passage isobviated.
 10. The apparatus according to claim 1, wherein the fluidprovided to the passage is hydraulic fluid.
 11. The apparatus accordingto claim 1, wherein the sleeve has a body with parts of differentdiameter, whereby a substantially constant backward force is applied tothe sleeve at system pressure.
 12. The apparatus according to claim 11,wherein the spool has a face exposed to hydraulic fluid which is of anarea to provide substantially constant force to the spool in a forwarddirection at system pressure.
 13. The apparatus according to claim 1,wherein the at least one seal comprises a plastics material.
 14. Theapparatus according to claim 1, further comprising separate seal(s) andport(s), whereby no port is passed over by any seal.
 15. The apparatusaccording to claim 1, further comprising a reciprocable device whichprovides reciprocal motion between the spool and the sleeve.
 16. Theapparatus according to claim 15, wherein the reciprocable device is aram weight mass.